Devices with touch sensitivity, typically combined with picture reproducing elements such as displays, are today used in a wide variety of applications such as touch pads in laptop computers, all-in-one computers, mobile phones and other hand-held and stationary devices.
There are numerous techniques for providing a device of the above kind with touch sensitivity, e.g. by adding layers of resistive wire grids or layers for capacitive touch-sensing. WO2008121908 discloses a system based on proximity sensing. Accordingly, the system comprises a touch panel where touch sensitivity is provided by internally emitted IR-light being reflected by e.g. a finger positioned on the touchable surface of the panel. Applicant's own international patent application WO2011049513 discloses a touch sensing system that uses frustrated total internal reflection (FTIR) to detect touching objects. More specifically, light emitted by a light source as well as ambient light is coupled into a light guide. This light then propagates inside the light guide by total internal reflection where after the transmitted light is received at an array of light detection points. The light may be disturbed (frustrated) by an object, such as a finger or a stylus, touching the light guide that acts as a touchable surface. This results in attenuation of the light signal, i.e. light intensity drops. This attenuated light is sensed at certain light detection points. The detected light is subsequently used to calculate different parameters associated with the object touching the guide.
Analogously to a conventional TV-set, it is often necessary to adjust different control parameters, such as brightness or contrast, of the device with touch sensitivity in order to enhance reproduction of the displayed picture. To this purpose, a plurality of dedicated buttons is normally provided on the device. Alternatively, said parameters may be adjusted by using a remote control (contracted “remote”), typically emitting signals in the infrared (IR) light range between 800 nm and 1000 nm. As an alternative, as implemented in the early days of the remote, visible light may be used to control the device.
Control signal emitted by the remote held by a user is received by a suitable sensor integrated in the device. Since remote signals require clear sight between sender and receiver and the user normally is positioned so as to see the display, i.e. the front side of the device, itself, said sensor is usually integrated in the frame of the display device so that the sensor eye faces the user. However, given the continuous quest for ever more reduced frame dimensions associated with devices with touch sensitivity, it is often undesirable to position the sensor on the front side of the device. Moreover, it is often perceived as aesthetically displeasing to position the sensor so that it may be freely seen by the users.
For these reasons, latest generation of display devices with touch sensitivity based on FTIR as disclosed in WO2011049513 have a sensor (an IR-sensor) positioned on the back side of the device. Front side as well as back side that shows the IR-sensor of such a device may be seen in FIGS. 1a and 1b, respectively. Such a solution is satisfactory at least in applications where frequent adjustment of control parameters is not required.
Another intrinsic property of the above-described control systems is the necessity to, in use, aim the remote rather precisely at the sensor eye. Obviously, from the user's perspective, this constraint is undesirable.
Further drawback of the conventional control systems is their sensitivity to external circumstances. More specifically, in case of the sensor being accidentally covered or soiled, the entire system becomes stripped of the remote functionality. Same is true in case of sensor breakage.
Previously mentioned WO2008121908 discloses, on a rather general and theoretical level, a touch sensitive system being remotely controllable without employment of a dedicated sensor. Even if the general knowledge in the field is taken into account, it is still unclear how the disclosed technical teaching should be practiced in order to achieve a functioning touch-sensitive system that also is remotely controllable without employment of a dedicated sensor.
Notwithstanding the above, WO2008121908 relates to a system comprising a touchable surface and an array of IR-sensors positioned at a distance from and parallel to the touchable surface. These sensors detect IR-light reflected from the object positioned above the touchable surface. This reflected light is, during its propagation in the interior of the device, scattered by the internal components, the functionality of the device thus becoming severely impaired.
Furthermore, WO2008121908 mentions, in a rather speculative fashion, a possibility of integrating a light guide into the touch panel by positioning it so that it guides light towards touchable surface. Nevertheless, in such a set-up, the array of IR-sensors would remain positioned at a distance from and parallel to the touchable surface and the light guide why the light that is detected by said IR-sensors cannot be the attenuated light that characterizes FTIR. On the contrary, such a set-up would result in detection of an intensified light signal, due to the fact that the object positioned on the touchable surface becomes a diffusive light source.
One objective of the present invention is therefore to provide an improved device with touch sensitivity that eliminates at least some of the drawbacks associated with the current art.